A method, signal processing device, front-end and Global Navigation Satellite System (GNSS) receiver of the generic type are known from, e.g., European Patent Application EP 1 983 351 A1, the entire contents of which are incorporated herein by reference. The method and devices are suitable for processing a signal restricted to a fixed frequency band as is the case with the Global Positioning System (GPS) signal which is a superposition of signals transmitted by the satellites pertaining to the GPS system. However, relying solely on the GPS signal can, particularly in special situations, be insufficient for determining a receiver position with a desired reliability and degree of precision. Quite often it may not be possible to receive signals from a sufficient number of satellites. In urban canyons, for instance, reception is often restricted to a rather small solid angle which may not contain a sufficient number of satellites. But even where the view of the sky is unobstructed, it may not be possible to receive signals from four or more different satellites as is usually required for a stand-alone determination of the receiver position. This is particularly true at high latitudes where, on average, fewer satellites are visible than in mid latitude and equatorial regions. But even where a sufficient number of satellites are visible, they may form a constellation, e.g., a cluster, which does not allow for a precise determination of the receiver position.